package com.jly.sqlSession;


import com.jly.pojo.Configuration;
import com.jly.pojo.MapperStatement;

import java.beans.IntrospectionException;
import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;

public class DefaultSqlSession implements SqlSession{


    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {

        //将要完成对simpleExecutor中query的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MapperStatement mapperStatement = configuration.getMapperStatementMap().get(statementId);
        List<Object> objects = simpleExecutor.query(configuration, mapperStatement, params);

        return (List<E>) objects;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {

        List<Object> objects = selectList(statementId, params);
        if(objects.size() == 1){
            return (T) objects.get(0);
        }else{
           throw  new RuntimeException("查询结果为空或者返回结果过多");
        }

    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //使用JDK动态代理为DAO接口生成代理对象,并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层还是执行JDBC代码，//根据不同情况调用selectList或者selectOne
                //准备参数 1、statementId sql语句唯一标识：namespace.id=接口全限定类名.方法名

                String name = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId = className+"."+name;
                //准备参数 2、params：args

                Type genericReturnType = method.getGenericReturnType();
                //判断是否进行了 泛型类型参数化
                if(genericReturnType instanceof ParameterizedType){
                    return selectList(statementId,args);
                }
                return selectOne(statementId,args);
            }
        });


        return (T) proxyInstance;
    }
}
